1. Field of the Invention
This invention relates to a liquid storing container for storing liquid therein, an ink jet head cartridge comprising an ink tank using the liquid storing container and a recording head for discharging ink, the ink tank and the recording head being connected together, and an ink jet recording apparatus in which the cartridge is removably mountable.
2. Related Background Art
Various containers have heretofore been available as a storing container for storing liquid therein, and above all, in the form of an ink tank for storing ink therein, a method as disclosed in U.S. Pat. No. 4,771,295 (Japanese Laid-Open Patent Application No. 63-87242) wherein an ink tank contains therein a porous member impregnated with ink is known as an ink storing method in an ink jet head cartridge (hereinafter sometimes abbreviated as IJC) comprising a recording head unit and a tank unit (an ink tank) made integral with each other.
However, in this method, for example, a sponge or the like which is a the porous member is impregnated with ink and therefore, it has been difficult to increase the volume efficiency beyond a predetermined level and further, negative pressure in the ink tank becomes greater with a decrease in the ink and a considerable quantity of unusable ink remains in the tank. This has led to the problem that it is difficult to increase the volume efficiency and value of the ink tank. Accordingly, it is difficult to increase the volume efficiency of the ink tank, the downsizing of the ink tank (liquid storing container) for storing a predetermined quantity of usable ink therein is difficult and the downsizing of the recording apparatus also becomes difficult.
On the other hand, to enhance the volume efficiency, it is preferable that ink be not absorbed in the porous member as described previously, but be directly contained. As a construction therefore, there is one as disclosed in U.S. Pat. No. 4,509,062(Japanese Laid-Open Patent Application No. 59-98857) or U.S. Pat. No. 4,500,895 (Japanese Laid-Open Patent Application No. 59-207263) wherein a bladder made of rubber is provided in an ink tank and ink is contained in the bladder.
However, in the case of such construction, the ink in the tank oscillates due to the movement or the like of a carriage as during recording and pressure fluctuation is caused to the ink supplied to a recording head and the quality of printing is deteriorated. Thus, it is still difficult to increase the volume of the tank. Also, negative pressure in the ink tank becomes greater with a decrease in the quantity of ink in the tank, and this also has led to the problem that the quantity of unusable ink remaining in the ink tank increases.
We have zealously carried on our studies to solve these problems and as a result, have proposed flow rate control means functioning also as a valve for stably effecting the supply and controlled shut-off of the ink to the head by a very simple construction. That is, flow rate control means functioning also as a valve comprising an elastic member having a slit adapted to be substantially closed in a steady state and to be opened for predetermined differential pressure or greater is provided in the ink tank. With such a device it is possible to effect the supply of the ink to the recording head with the pressure of liquid which is applied to the nozzle of the recording head being controlled to a predetermined range.
More specifically, a dome-shaped or semispherical partition wall (hereinafter referred to as the slit bladder) having a valve function in which when the difference between internal pressure and external pressure reaches a predetermined value or greater, the wall is deformed to thereby open the slit and for certain differential pressure or lower, the wall restores its original state to thereby close the slit is provided in the ink tank or an ink flow path. An example of an ink jet head cartridge comprising an ink tank of such a construction and a head connected together is shown in FIG. 14 of the accompanying drawings. In FIG. 14, the reference numeral 900 designates a recording head unit, the reference numeral 901 denotes a slit bladder, the reference numeral 902 designates a slit, the reference numeral 903 denotes a sub-tank, the reference numeral 905 designates a main tank, and the reference numeral 906 denotes an ink bag. By such a construction, it has become possible to provide an ink tank of large capacity which can accomplish the stable supply of ink from the ink tank to the head.
We have carried on experiments to further improve the liquid storing container or the ink tank having such a slit bladder and have found the following fact.
Generally, when use is made of a hermetically sealed system ink tank, it is necessary to take care of the solidification of ink. That is, when the ink tank is kept or left at a low temperature which will solidify ink, the deformation of the slit bladder which has produced predetermined negative pressure by the volume expansion by the freezing of the ink inside and outside the slit bladder (the inside: the subtank; the outside: the main tank) is gradually eliminated, and when the pressure in the slit bladder is further heightened by the freezing of the ink, this pressure propagates to the recording head unit, whereby the ink may leak from the nozzle surface of the recording head.
To avoid this, there is a method whereby, for example, a solution having a low solidifying point such as ethylene glycol is mixed with the ink solution to thereby prevent the freezing of the ink at low temperatures. The adoption of such a method, however, may increase the blur of the ink when the ink arrives at paper to thereby deteriorate the quality of printing. To suppress the blur, paper exclusively for use with such method becomes necessary and therefore, an ink tank, a head cartridge, etc. which can sufficiently cope with the preservation of ink at low temperatures have been desired.